Background and Aims:
Although the dramatic rise in rates of autism spectrum disorder (ASD) could be attributed in part to changes in ASD definition and increase in awareness, increase in prevalence of certain non-genetic pre- and perinatal risk factors might also be implicated.

Methods:
We conducted a historical cohort study to examine the association between obstetric procedures (cesarean section [CS], assisted delivery, and induction by pitocin) with risk of ASD. The cohort consisted of the national birth and autism databases of Norwegian's National Health Insurance Registry (N=2,234,392 live births). We used logistic regression models to compute odds ratios (OR) and 95% confidence intervals (95%CI) for ASD for every obstetric procedure vs. all births in which the specific procedure was not applied. Data were stratified on sex and gestational age for all procedures, and on type of surgery (elective vs. emergency) for CS.

Results:
We found a 67% increase in ASD risk among children born by CS compared to vaginal delivery (95%CI, 1.48-1.88; p<.001). The association was independent of type of surgery and persisted after stratification by gestational age categories. An increased risk for ASD was also observed in forceps-assisted deliveries, but was limited to male post-term newborns. No association was found between vacuum extraction or pitocin induced labor and ASD.

Conclusions:
Both elective and emergency CS were found to be associated with risk of ASD across gestational ages. This finding is consistent with some of the previous studies and might help identify newborns at risk for ASD, and might also have potential implications for risk reduction.

10 - ASSISTED DELIVERY AND CESAREAN SECTION AND RISK OF AUTISM SPECTRUM DISORDER